The city’s formerly toothless Human Rights Commission has been walloping offenders with rec­ord high fines — yet is on pace to close the fewest number of cases in nearly a decade, records show.

The average settlement won for complainants grew from $11,358 to $50,434 in last six months of 2015, compared to the same period the previous year, according to data from the Mayor’s Office of Operations.

Civil penalties paid to the city also hit record highs in recent months.

At the same time, the agency closed just 150 cases in the second half of 2015 — down more than 65 percent from the 433 closed in the last half of 2014.

Agency officials attributed the drop — which came despite an infusion of $3.4 million from the city to add 54 full-time staffers to the agency in 2015 — to a boost in the number of cases opened.

“Commissioner [Carmelyn] Malalis’ aggressive efforts to support victims of discrimination are reflected in the department’s 31 percent increase in investigations [in 2015] and increase in fines, which are intended to deter egregious violators,” said spokesman Seth Hoy.

The last time the agency closed fewer than 300 cases in a full year was in fiscal 2007, records show.

The more than tripling of awards for complainants began just months after Malalis replaced Bloomberg administration holdover Patricia Gatling as commissioner starting in March 2015.

Last week, Malalis unilaterally decided to quadruple an administrative judge’s recommendation of a $25,000 fine against Manhattan real-estate firm Best Apartments, which the judge found had discriminated against a tenant seeking to pay with a federal Section 8 housing voucher.

In her decision, Malalis said Best’s refusal to show up for hearings and its vast size merited a $100,000 penalty — the highest ever for housing discrimination.

In November, the new commissioner imposed an unprecedented $250,000 civil penalty against an 86-year-old small-business owner accused of multiple instances of sexual harassment — the highest civil penalty ever and the maximum allowed.

In that case, Malalis had more than tripled the $75,000 fine approved by the judge against Automatic Meter Reading Corp. owner Jerry Fund.

A lawyer for the firm, Jonathan Honig, filed a lawsuit in Manhattan Supreme Court on Nov. 25 charging that the record fines — including $200,000 in emotional damages — were “arbitrary and capricious.”